The measurement of mechanical properties using specimens whose minimum dimensions are on the order of micrometers is an important new area of experimental solid mechanics. One obvious application is in the area of microelectromechanical systems (MEMS) where the final product is on the millimeter or micrometer size scale. Efforts to characterize the small scale mechanical properties of materials result from the desire to accurately and reliably model the performance of MEMS and other small scale devices.
The desire to measure properties such as the modulus of elasticity, yield strength, ultimate tensile strength, failure strength, and elongation at failure is critical for designing, modeling behavior, and predicting the performance of components.
Testing materials at the microscale is very different from familiar macro property mechanical characterization tests. Miniaturizing the specimens creates many challenges in testing them, such as specimen preparation and gripping, applying forces, measuring displacements or strains, and eliminating the test structure and machine's deformation and displacements. In a specimen as small as 200 microns, 1 micron deformation indicates 0.05 strain. Therefore measuring displacement at the submicron level is critical in tests at these small scales. A few techniques have been developed to measure the strain and displacement in small specimens, such a capacitive gauges, eddy current sensors, and laser micrometer systems. These accurate sensors can be mounted on the test machine to measure displacements. The place the sensor is mounted is very important in obtaining accurate test results. The errors that may be introduced in measurements are due to test fixture deformation, cross head deformation, load cell deformation and tolerances of the test fixture. For instance, a few microns deformation in the load cell will result in a completely inaccurate capacitive gauge measurement, thus making the position of the capacitive gauge critical.
The properties of thin films and materials with micron size dimensions are not necessarily the same as their bulk counterparts, thus there is a clear need for accurate miniaturized mechanical test fixtures and measurement devices.